Increasing the v.i. of hydrocracked light lubes

ABSTRACT

A process for increasing the V.I. of a light lube fraction approximating the viscosity range of a 100 Neutral oil which has been hydrocracked as part of a relatively wide-range lube fraction wherein the light lube fraction is isolated and rehydrocracked in the absence of heavier fractions.

United States Patent Inventors Sheldon L. Thompson Glen Mills;

Albert T. Olenzak; Rene F. Kress, Media, Pa.; Ib Steinmetz, Wilmington,Del. 780,241

Nov. 29, 1968 Nov. 2, 1971 Sun Oil Company Philadelphia, Pa.

INCREASING THE V.l. OF HYDROCRACKED LIGHT LUBES 5 Claims, No DrawingsInt. Cl C 10g 37/02 Field of Search 208/19, 59, 264, 18

Primary Examiner-Herbert Levine Attorneys-George L. Church, Donald R.Johnson, Wilmer E.

McCorquodale, Jr. and Harold M. Dixon ABSTRACT: A process for increasingthe V.l. ofa light lube fraction approximating the viscosity range of a100 Neutral oil which has been hydrocracked as part of a relativelywiderange lube fraction wherein the light lube fraction is isolated andrehydrocracked in the absence of heavier fractions.

Neutral oil, derived from hydrocracked lubricating oil product bysubjecting said isolated fraction to a second hydrocracking treatment.

BACKGROUND OF THE INVENTION Various processes have been used from timeto time for upgrading lubricating oil stocks. These have generallyinvolved either solvent extraction or hydrogenation includinghydrocracking treatment. In more recent times, there has been a demandfor lubricating oils having an increased viscosity index. Recentdevelopments, particularly in hydrocracking techniques, or hydrotreatingtechniques, as some prefer to call it, have given birth to an increasedinterest in commercial utilization of such hydrogenation processes as alubricatingoil-stock-upgrading method to obtain lubricating oils with anincreased viscosity index. Briefly, this has involved catalytichydrocracking of the lubricating oil stock at a temperature on the orderof about 650 F. and above at high partial pressures of hydrogen. Thelube stocks that are hydrocracked are also subjected before and afterthe hydrocracking to many of the conventional refining operations. Amongthese is the substantially final step of fractionating or distilling thelube stock into various fractions according to viscosity which can thenbe blended to obtain a particular desired viscosity. The first fractiontypically has an S.U.S. viscosity of about 100 and 100 F. and a boilingrange of about 700 to 800 F. This is usually referred to in the industryas 100 Neutral. While hydrocracking processes have greatly enhanced theviscosity index of the lubricating oil stocks so treated, on occasion atleast certain fractions and especially the lighter fractions (e.g., 100Neutral) are somewhat lower in viscosity index than the heavierfractions. It is desirable that the lighter fractions be ofsubstantially the same V.I. as the heavier fractions. Typically, thelighter and first fractions comprise about one-third of the totalfinished lube product. Therefore, it is quite important that it have afully satisfactory character such as viscosity index. It would be highlyadvantageous to provide a method for enhancing the viscosity index ofthe lighter fractions of hydrocracked lube oil product. It is thereforea primary object to prepare lubricating oils in high yields and having ahigh V.I. and particularly the lighter fractions or 100 Neutral productof a finished lube stock. It is another object to accomplish the V.I.enhancement without undue adverse effects on the other properties of theoil. It is still a further object to accomplish the objects of thisinvention in a relatively economical fashion. Other objectives willbecome apparent from the comments found herein.

SUMMARY OF THE INVENTION To the accomplishment of the foregoing andrelated ends a paraffinic-base lube oil stock which has beenhydrocracked over a hydrocracking catalyst at a temperature above about650 F. under high pressure is fractionated into a first cut boiling inthe range of about 700to 800 F. and a viscosity of about I at 100F., andsaid hydrocracked fraction boiling in the range of about 700to 800 F. isthen separately rehydrocracked under substantially the same conditionsas the total charge in the first step, and finally the rehydrocrackedproduct fraction is recovered. When recovered, the rehydrocrackedfraction has an enhanced V.I.

The results obtained by this invention are unexpected since the sameviscosity index enhancement of the lighter fraction or I00 Neutral isnot realized if it is recycled in contrast to the present inventiveprocedure of the isolation and the separate rehydrocracking of the 100Neutral fraction in the absence of substantial amounts of heavierfractions.

The broad and preferred conditions of the hydrocracking operation, someof the soluble feedstocks, conventional operations which are to becarried out, and equally important, which conventional operations can orare to be omitted are described in great detail in U.S. Pat. No.2,960,458. The teachings of that patent are incorporated here inentirety but with certain important variations that will be foundhereinafter. As a matter of convenience to the reader, a relativelybrief summary of certain of the teachings of that patent are set forthhereinbelow.

These teachings of the patent comprise the following: A deasphaltedresiduum having a V.I. in the range of about 75 and 100 and a viscosityat 210 F. in the range of about to 200 S.U.S. is treated with hydrogenat a temperature between about 650and 825 F. but preferably betweenabout 735and 825 F. at a pressure of at least about 1,500 p.s.i. butmore usually and preferably above about 2,500 and at a space velocitybetween about 0.2 and 4.0 but more usually about 0.4 and 1.5. Thetreatment with hydrogen is carried out in the presence of a catalysthaving both aromatic saturation and ring-scission activity, whichbroadly comprises a sulfide of any metal of Group VI, left-hand column,of the periodic system mixed with an iron group metal, for example, anickel sulfide and tungsten sulfide catalyst in about a l:l to 4:] metalratio. The product from the hydrogen treatment is subjected to dewaxing(when necessary) and is then distilled to yield components most of whichdirectly, or upon blending with each other, meet the SAE specificationsfor a multigrade lubricating oil and have a V.I. of about and preferablyor above.

U.S. Pat. No. 2,960,548 teaches that in order to obtain suitable yieldsof multigrade oils having the desired viscosity it is essential toemploy as the charge to the hydrocracking reactor residual-type chargestocks; however, in the present invention at least, vacuum distillates,Duo-sol extracted residuum, residuums extracted with a solvent havingpreferential solubility for aromatics such as furfural and phenol, orblends of the foregoing are also suitable. The procedures for carryingout the extraction can be found in copending application Ser. No.743,915 filed July 3, 1968, by Rene F. Kress. The charge should have aninitial boiling point at above about 650 F. and preferably about above700 F. The residuum starting material, however, can be any residuumobtained by atmospheric or vacuum distillation, or the like, of anypetroleum or residual fraction thereof which after deasphalting,preferably with a low-boiling hydrocarbon such as propane, propylene, orbutane, has a V.I. of 75 to 100 and a viscosity at 210 F. of about 45 to200 S.U.S. but is preferably above 50 S.U.S and still more preferably atleast about 90 S.U.S. Thus, for instance, the residuum may be preparedby vacuum distillation of a Pennsylvania, Mid-Continent, West Texas,Kuwait. etc., crude. Unlike U.S. Pat. No. 2,960,458, deasphalting withagents such as sulfuric acid, phenol, sulfur dioxide, etc., in thepresent invention does not necessarily result in removal of componentswhich upon hydrogenation have desirable properties for a multigrade oilproduct. In this invention if these materials are employed for asphaltremoval, the product produced in some cases is of as good or betterquality; and the yield of multigrade oils is the same or even better insome cases. A higher carbon residue will result in undesirableshortening of the life of the catalyst under the relatively severehydrogen treatment conditions employed to produce the multigrade oil.For this reason, it is usually preferred to employ charge stocks havinga low-carbon 2 such as below about 2 (Conradson). However, higher carbonresidue charge stock may be used if catalyst life is not of greatimportance or if a rugged catalyst is used. The utilization of chargestock having a V.I. of 75 to 100 is essential in obtaining a reasonableyield ofa multigrade lubricating oil; i.e., a V.I. of above about 100 isproduced in good yield only if a charging material of at least about 75V.I. is employed. It will result in drastically lower yields if a lowerthan 75 V.I. charge stock is used. Unlike U.S. No. 2,960,458, aviscosity of between about 90 and 200 S.U.S.

at 210 F. is not absolutely required as the viscositymay be as low asabout 45 S.U.S. but preferably is above about 50 S.U.S. at,2 F. The onlyimportant difference in using a feed having a viscosity below about 90S.U.S. at 210 F. is the product viscosity and product distribution. Whena feed having a viscosity below about 90 S.U.S., for example, about 60S.U.S., is charged, a full range of the conventionally desired blendstocks will not be obtained. Unless the feed has a viscosity of at leastabout 45 S.U.S., there will be little if any lube fraction producedhaving a viscosity in the range of a 200 Neutral oil; and the problem ofadjusting reaction conditions to produce a 100 Neutral oil with asatisfactory V.l. will not be encountered. At viscosities below about 45S.U.S. the only lube oil product is essentially one that is in theviscosity range of a 100 Neutral oil. A substantial amount of lightermaterial is, of course, simultaneously produced. As the viscosityincreases above about 45 S.U.S., the problem of producing a 100 Neutralbecomes more difficult; and as a consequence thereof, the need for thisinvention increases. To the extent that it is most frequently desired toproduce a lube product containing the full range of conventionalblending stocks for maximum flexibility in blended product viscosities,this invention is most advantageously and preferably employed with feedshaving a viscosity of about 90 to 200 S.U.S. at 210F.

In many cases the lighter or l00 Neutral fraction obtained from theforegoing hydrocracking procedure does not exceed about I00 V.l. or iseven less. Where the lighter fractions V.l. is desirably higher,according to the present invention, it alone is rehydrocracked at theforegoing conditions employed in the first hydrocracking step. Thepreferred conditions in the initial hydrocracking treatment areespecially preferred in rehydrocracking the 100 Neutral fraction. inorder to provide fullness of disclosure, the conditions for therehydrocracking of the No. l distillate fraction will now be set forthalthough they are the same as the initial hydrocracking conditionsemployed for the total original feedstock.

ln brief, the procedure comprises charging the No. l distillate withhydrogen at a temperature between about 650and 825 F., preferablybetween 700and 800 F., and most preferably in the range of about 735to775 F., a pressure above 1,500 psi. but more usually and preferablyabout 2,500, and a space velocity between about 0.2 and 4.0 but moreusually about 0.4 and 1.5. The treatment with hydrogen is carried out inthe presence of a catalyst having both aromatic saturation andring-scission activity, which broadly comprises a sulfide of any metalof Group Vl, left-hand column, of the periodic system mixed with an irongroup metal, for example, a nickel sulfide and tungsten sulfidecatalyst, in about a 1:1 to 4:1 metal ratio. Other variations of thehydrocracking process are well known or suggested in the art and are tobe considered included within the scope of this invention. Examples ofsuch are those described in U.S. Pat. No. 2,917, 448 to Beuther et al.;U.S. Pat. No. 3,046,218 to Henke et al., U.S. 3,222,272 to Bercik et al.Especially important variations are the improved catalysts described inU.S. Pat. No. 3,078,221 to Beuther et al. and U.S. Pat. No 3,078,238 toBeuther et al. In addition, other variations are known and of catalystsin particular. An example is the suitability of catalysts which are notsulfactive by a proper pretreatment of the feed to remove or convertsulfur and nitrogen compounds to the harmless form. Such catalystsinclude platinum and palladium metals. Preferably, these and allsuitable catalyst metals are employed in the sulfided form.

ILLUSTRATIVE EXAMPLES A charge stock of grade B solvent lube crude mixwas charged to a crude still and fractionated into approximately 70percent and 30 percent of overhead and bottoms, respectively. Thebottoms had an initial boiling point at 650 F. at atmospheric pressure.The bottoms were charged to a vacuum still and fractionated to produce agas oil, a distillate stock, and a residual asphalt stock, the lattertwo having initial boiling points of about 695 F. and 750 F.,respectively. The residual stock was deasphalted and extracted by theDuo-Sol process (which employs propane'and a mixture of phenalcresol assolvents) at approximately 130F. The raffinate from the deasphalter andthe distillate'stock from the vacuum still when combined had thefollowing properties:

TABLE 1 Gravity, API 30.5 Vacuum Distillation Range at 2 mm. Adjusted to760 mm.

Initial 694 70% 964 E.P. 1,030 Recovery, 83 Aniline Point 239.2SUS/2l0F. 59.7 Average M. W. 505 Wt. Aromatics 22.4

Viscosity index The foregoing mixture was charged to a hydrocracker, andsaid material was hydrocracked in the preferred manner described in U.S.Pat. No. 2,960,458, i.e., at the preferred conditions and using apreferred nickel-tungsten sulfide catalyst set therein. A hydrogenstream comprising gas and hydrogen, of which about 85 percent washydrogen, was used in the hydrocracking reaction.

The crude hydrocracked product was charged to a stripper or atmosphericstill and fractionated to produce gas, naphtha, and fuel oil, and a waxylube of initial boiling point of approximately 700F.

At this point a total product of about 105 average V.l. was obtained (ona dewaxed basis), However, the V.l.'s of the separate lube fractions (ona dewaxed basis) were:

Neutral I00 200 Neutral I08 500 Neutral I05 Brightstock l06 The totalfraction was dewaxed, and a 100 Neutral fraction was separated andpassed through a second hydrocracking reactor.

The product from the second hydrocracking was charged to a stripper orstill and light ends removed to produce a 100 Neutral fraction. Theyield based on 100 Neutral charged was 75 percent. The details of thehydrocracking conditions in each of the hydrocracking steps as well asthe resulting V.l. were as follows:

l. A process comprising hydrocracking a lube oil charge stock boilingabove about 650 F., at from about 735 to 825 F and a hydrogen partialpressure of at least 1,500 p.s.i. to produce a hydrocrackate, separatinga fraction boiling at from about 700 to 800 F. from said hydrocrackateand separately secondly, hydrocracking said fraction substantially byitself at from about 735 to 775 F. and a hydrogen partial pressure of atleast about 1,500 p.s.i. and recovering from said second step recoveringa lube oil having an enhanced viscosity index and boiling in the rangeof about 700 to 800 F., wherein the space velocity in both hydrocrackingsteps is from 0.4 to 1.5.

2. The process of claim 1 wherein both hydrocracking steps are carriedout in the presence of a catalyst which is a sulfactive metal of atleast one member of the group consisting of Group Vl b and Group VIII bof the periodic table.

3. The process of claim 2 wherein the oil boiling in the range of fromabout 700 to 800 F. is recovered from the second hydrocracking step inabout a 75 percent yield as based on the oil charge to said secondhydrocracking step.

4. The process of claim 3 wherein the catalyst in both hydrocrackingsteps is a combination of at least two members of the group consistingof nickel sulfide, tungsten sulfide, cobalt sulfide, and molybdenumsulfide,

5. The process of claim 4 wherein the catalyst in both hydrocrackingsteps is a combination of nickel sulfide and tungsten sulfide in a metalratio of from 1:1 to 4:1 nickel:tungsten supported on an aluminacarrier.

2. The process of claim 1 wherein both hydrocracking steps are carriedout in the presence of a catalyst which is a sulfactive metal of atleast one member of the group consisting of Group VI b and Group VIII bof the periodic table.
 3. The process of claim 2 wherein the oil boilingin the range of from about 700* to 800* F. is recovered from the secondhydrocracking step in about a 75 percent yield as based on the oilcharge to said second hydrocracking step.
 4. The process of claim 3wherein the catalyst in both hydrocracking steps is a combination of atleast two members of the group consisting of nickel sulfide, tungstensulfide, cobalt sulfide, and molybdenum sulfide.
 5. The process of claim4 wherein the catalyst in both hydrocracking steps is a combination ofnickel sulfide and tungsten sulfide in a metal ratio of from 1:1 to 4:1nickel: tungsten supported on an alumina carrier.